1. Field of the Invention
The present invention is generally in the field of semiconductors. More particularly, the invention is in the field of semiconductor memory arrays.
2. Background Art
A memory array, such as a programmable read-only memory (ROM) array, can include a number of memory cells, where each memory cell includes a fuse that can be electrically blown to program the memory cell. During programming of each memory cell in the array, a programming voltage, which is typically provided by a charge pump, can be applied to the fuse via a programming device so as to cause the fuse to break down. However, the level of the programming voltage required to break down a conventional fuse, such as a conventional polysilicon (poly) gate fuse, can undesirably increase leakage current in the memory array.
A conventional fuse, such as a conventional poly gate fuse, can include a gate oxide layer underlying a poly gate. During memory cell programming, a high voltage can be applied to the poly gate to cause the gate oxide layer to break down, thereby shorting the gate to the substrate. However, the level of high voltage required to cause the gate oxide layer to breakdown can increase leakage current in high voltage charge pumps and programming devices in the memory array, which can undesirably limit the size of the array. Also, as a result of temperature and voltage stresses, the resistance of the gate oxide layer in a conventional fuse, such as a conventional poly gate fuse, can change after the memory cell has been programmed. As a result, a memory cell utilizing conventional fuses, such as conventional poly gate fuses, can change logic states after being programmed, thereby undesirably reducing memory array reliability.